A continuing interest exists in industry for a simple, highly efficient gas compressor. Such devices may be useful in a variety of applications. Operational costs could be substantially improved in many applications by adoption of a compressor that provides improvements in operating efficiency as compared to prior art compressor designs. Further, from the point of view of maintenance costs, it would be desirable to develop new compressor designs that reduce the mass of rotating components, since rotating components have generally been identified as comparatively costly when replacement or repair becomes necessary, as compared to non-rotating parts which are subject to stress and strain from temperature and pressure, but not to additional loads due to rotary motion. Thus, it can be appreciated that it would be advantageous to provide a new, high efficiency compressor design which minimizes moving parts.
Although a variety of supersonic compressors have been contemplated, and some have been tested by others, the work of J. K. Koffel et al. as reflected in U.S. Pat. No. 2,974,858, issued Mar. 14, 1961, and entitled “High Pressure Ratio Axial Flow Supersonic Compressor,” the disclosure of which is incorporated herein in its entirety by this reference, is instructive of such work generally, and thus is suggestive of technical problems that remain in the field and with respect to which better solutions are required in order to improve operational capability and compression efficiency. Although the Koffel et al. patent describes the use of an impulse blade rotor and illustrates a downstream bladed stator, the compressor geometry described would appear, maximally, to only enable achievement of pressure ratios stated therein, which are at one point mentioned as an “ . . . overall pressure ratio of approximately 4 to 1 in a single rotor-stator stage.” And, although the Koffel et al. patent mentions issues with respect to boundary layer effects, it does not provide for integrated control of such phenomenon as may be useful to avoid perturbations caused by boundary layer interaction with shock waves, especially as might be applied for compressor operation at higher pressure ratios than those noted therein.
In short, there remains a need to provide a design for a high pressure ratio supersonic compressor that simultaneously resolves various practical problems, including (a) providing for starting of a compressor designed for high pressure ratio operation so as to control a normal shock at an effective location in a supersonic diffuser designed for high pressure ratio and efficient compression, (b) avoiding excessive numbers of leading edge structures (such as may be encountered in prior art multi-bladed stators), and minimizing other losses encountered by a high velocity supersonic gas flow stream upon entering a diffuser, and (c) providing for effective boundary layer control, especially as related to retention of a normal shock at a desirable location, in order to achieve high compression ratios in an efficient manner.